1. Technical Field
The present invention relates to an image processing device that forms images on checks, recording paper, and other sheet media or reads images on the sheet media, and relates more particularly to a sheet feeder mechanism for separating and feeding sheets stored in a stack in the device into the sheet conveyance path.
2. Related Art
Image processing devices of this type normally have a media separation mechanism that prevents multifeeding of sheets stored in a stack into the sheet conveyance path. Japanese Unexamined Patent Appl. Pub. JP-A-2009-18891 teaches a mechanism that uses a retard roller as an example of such a media separation mechanism. This mechanism causes the sheets to be conveyed between a feed roller and a retard roller, which is pressed against the feed roller with a rotational load applied thereto. When overlapping sheets pass together between these rollers, the frictional force produced between the sheet on the retard roller side and the retard roller restricts feeding the sheet on the retard roller side.
In order to keep the pressure load of the retard roller on the separation roller at a desirable level, the counterforce of the sheet on the retard roller is supported by a guide surface for sliding the retard roller in a direction intersecting the sheet feeding direction. By using this construction, the retard roller support structure of JP-A-2009-18891 is made more complicated and the retard roller cannot be easily replaced.
As a result of producing a strong braking force, the retard roller also wears quickly. Such wear reduces the nipping strength and reduces the brake power, and is also related to problems such as sheet multifeeding and sheets not being fed. When this happens, the service life of the sheet feeder mechanism or the image processing device can also be affected if the retard roller cannot be easily replaced.
This problem is common to sheet feeder mechanisms and image processing devices that have a retard roller, and an object of the invention is to easily eliminate a drop in performance when the retard roller becomes worn.